A dual-energy radiation detector is an apparatus that detects radiation in a low-energy range and radiation in a high-energy range transmitted through a specimen (refer to, for example, Patent Document 1). According to such a radiation detector, by simultaneously obtaining a radiation image in the low-energy range and a radiation image in the high-energy range and preparing, based on those radiation images, a processed image applied with a predetermined processing (for example, a weighted subtraction, superimposition, or the like), detection of a foreign substance, measurement of the component distribution, measurement of the weight, and the like can be realized at high accuracy in a non-destructive inspection (that is, an in-line non-destructive inspection) of the specimen that is conveyed by a conveyor or the like.    Patent Document 1: Japanese Published Examined Patent Application No. H05-68674